im still learning the functions on my 350D, i think the trick is to pevent yourself from using the automatic mode and force yourself to try and acheive your desired picture using aperature priority, shutter priority or full manual... eventually you start to get an idea of where all the options are and what they do...
misty water is all about slow shutter speed
you can achieve this by:
keeping the aperature up as low as it will go ( F22ish ) and keep the ISO as low go also ( ISO100ish )
if tis too bright and your still not getting it misty enough its time to break out a nuetral density filter